Electro-physiology (1896-98) Electro-physiology electrophysiolog01bied Year: 1896-98 IV ELECTROMOTIVE ACTION IX MUSCLE 335 current, it is of course easy to measure the intensity of the muscle current; yet, in view of the great and very variable resistance of vegetable and animal tissues, such measurements an- on the whole of little value. Much greater importance attaches on the other hand to exact measurements of electromotive force. If two points of different potential are connected !>y a leading- off circuit to a conductor which is the seat of electromotive force, a branch of the current
Electro-physiology (1896-98) Electro-physiology electrophysiolog01bied Year: 1896-98 IV ELECTROMOTIVE ACTION IX MUSCLE 335 current, it is of course easy to measure the intensity of the muscle current; yet, in view of the great and very variable resistance of vegetable and animal tissues, such measurements an- on the whole of little value. Much greater importance attaches on the other hand to exact measurements of electromotive force. If two points of different potential are connected !>y a leading- off circuit to a conductor which is the seat of electromotive force, a branch of the current will flow through these, of intensity directly proportional with the which may be conceived as acting at the points of junction. The magnitude of the latter may thus be measured from the difference in potential between two points led off, and where it is possible to determine this exactly, it is also possible to determine the magnitude of the electromotive force. And the of the longitudinal current could be ascertained simply by measuring the ;. between natural longitudinal surface and artificial cross-section. The dif- ference of potential between two G points is easy to determine ex- perimentally, by a method in- vented by Poggendorff, and essen- . 11 -11 n TJ •„ FIG. 10(3.—Measurement of by com- tially improved by du Bois- peiisation_ (Du ) Eeymond (8). The principle of the method is to replace the magnet from its deflected position to its original position of rest, by means of a fraction of the current of a standard cell, opposing and cancel- liner the original current. The known variable is thus O O a measure for the magnitude of the unknown difference to be determined. Such a ' compensating' current can easily be derived from a measuring circuit by means of a rheochord, termed in this case a ' compensator.' If a constant current (A') is led through a straight or circular wire (Fig. 106 a, b), a definite ' electrical fa
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